JPH1193964A - Constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost of material in a holder, and attain simplification of a work process. SOLUTION: A holder 4 is a ring unit comprising a spherical external diametric surface 4a contact guided by an internal diametric surface of outer side joint member, spherical internal diametric surface 4b contact guided by an external diametric surface of inner side joint member, and a plurality of pockets 4c receiving a torque transmitting ball. Spherical center of the external diametric surface 4a and that of the internal diametric surface 4b are respectively offset relating to the center of the pocket 4c to an opposite side by an equal distance in an axial direction. The holder 4 uses carbon steel as a material, after work in prescribed shape, an austempering process is applied as heat treatment, and as necessary, work (grinding work or the like) for ensuring accuracy is applied to the external/internal diametric surface 4a, 4b to be finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant velocity universal joint used for power transmission in automobiles and various industrial machines.

[0002]

2. Description of the Related Art Constant velocity universal joints are roughly classified into a fixed type that allows only angular displacement between two axes and a sliding type that allows angular displacement and axial displacement.
The model is selected according to the application. The fixed type is typically a Zepper type constant velocity universal joint, and the sliding type is typically a double offset type constant velocity universal joint. In each case, a ball is used as a torque transmitting member, which is housed in a pocket of a retainer. .

[0003] For example, in a double offset type constant velocity universal joint, a cage having a configuration in which the center of the spherical surface of the outer diameter surface and the center of the spherical surface of the inner diameter surface are respectively offset by the same distance in the axial direction from the center of the pocket. used. When this type of joint transmits rotational torque while maintaining an operating angle, the retainer rotates to the position of the torque transmitting ball moving on the ball track according to the inclination of the inner joint member, and rotates the torque transmitting ball to the operating angle. At an angle bisecting plane. Thereby, the constant velocity of the joint is ensured. Also, when the outer joint member and the inner joint member move relative to each other in the axial direction, a slip occurs between the outer diameter surface of the retainer and the inner diameter surface of the outer joint member, thereby enabling smooth axial movement (plunging). To

Conventionally, the above-mentioned retainer for a constant velocity universal joint is made of chromium steel as a raw material, processed into a predetermined shape, then carburized to ensure strength, durability and abrasion resistance, and further subjected to accuracy. (External diameter surface, internal diameter surface, etc.) are finished to predetermined dimensions by grinding.

[0005]

The conventional constant velocity universal joint retainer has the following points to be improved.

[0006] Since the heat treatment is performed by the carburizing treatment, the deformation due to the heat treatment is large, and the dimensional variation is not stable. Therefore, it is necessary to perform finishing by grinding after the heat treatment.

The pocket surfaces on both sides in the axial direction of the pocket,
The required accuracy is required for controlling the position of the torque transmitting ball, but the grinding after the heat treatment is often omitted in order to simplify the working process. In that case, if the heat treatment deformation was large, it was regarded as a defective product, and therefore the defect rate was large.

[0008] Conventionally, the cage has the strength and durability of the material,
In terms of abrasion resistance, it has enough performance,
There is room for reconsideration in both materials and processing steps.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the material cost of a cage for a constant velocity universal joint, to simplify a working process, and to reduce the cost of a constant velocity universal joint.

[0010]

In order to solve the above-mentioned problems, the present invention employs carbon steel as the material of the cage and employs austempering as a heat treatment.

As the "carbon steel", a carbon steel appropriately selected from carbon steels for machine structures (S10C to S58C) specified in JIS can be used.

"Austempering" is a kind of quenching method utilizing the S curve of steel, in which the steel heated to the austenite region is maintained at a bainite formation temperature (a temperature range below the nose of the S curve). This is a heat treatment method in which the steel is quenched in a salt bath or a lead-bismuth bath, where the structure is maintained until the structure is completely changed to bainite, removed from the bath, and cooled to room temperature. If the holding temperature in the heat bath is high, upper bainite with feathery structure is generated, and if the holding temperature is lower, lower bainite with needle-like structure is generated.

In the austempering treatment, the heat-treated deformation of the treated product is smaller than that of the heat treatment such as carburizing. Also, quenching
Since only two heat treatment operations of tempering are required, the total time required for heat treatment is short. In addition, the austempering process transforms the structure of carbon steel into bainite,
It becomes a material with excellent toughness.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a double offset type constant velocity universal joint as a sliding type constant velocity universal joint according to this embodiment. The constant velocity universal joint includes an outer joint member 1 having a plurality of (for example, six) linear guide grooves 1b formed in a cylindrical inner diameter surface 1a in an axial direction, and a plurality of (for example, a spherical outer diameter surface 2a). The inner joint member 2 in which six (6) linear guide grooves 2b are formed in the axial direction, and the ball track formed by the cooperation of the guide groove 1b of the outer joint member 1 and the guide groove 2b of the inner joint member 2. (For example, six), and a retainer 4 for holding the torque transmitting balls 3.

As shown in FIG. 2 in an enlarged manner, the retainer 4
A spherical outer diameter surface 4a guided in contact with the inner diameter surface 1a of the outer joint member 1, a spherical inner diameter surface 4b in contact with the outer diameter surface 2a of the inner joint member 2, and a torque transmission ball 3 are accommodated. And a plurality of (for example, six) pockets 4c. A pillar 4d is provided on both circumferential sides of the pocket 4c, and an entrance 4e for incorporating the inner joint member 2 is provided on one axial side. The center of the spherical surface of the outer diameter surface 4a and the center of the spherical surface of the inner diameter surface 4b are offset by the same distance in the axial direction from the center of the pocket 4c.

When the joint transmits the rotational torque while maintaining the operating angle θ, the retainer 4 rotates to the position of the torque transmitting ball 3 moving on the ball track according to the inclination of the inner joint member 2, and the torque is reduced. The transmission ball 3 is held at an angle bisecting plane (θ / 2) of the operating angle θ. Thereby, the constant velocity of the joint is ensured. When the outer joint member 1 and the inner joint member 2 relatively move in the axial direction, the outer diameter surface 4
a between the outer joint member 1 and the inner surface 1 a of the outer joint member 1,
Enables smooth axial movement (plunging).

The cage 4 is made of carbon steel, processed into a shape as shown in FIG. 2, and then subjected to an austempering treatment as a heat treatment in order to secure strength, durability and abrasion resistance. The outer diameter surface 4a and the inner diameter surface 4b
The workpiece is processed (grinding, etc.) to ensure accuracy. For example, an S53c material is used as carbon steel, and the conditions of the austempering treatment are set to (880 ° C. ×
1.5 hours) → (305 ° C. × 2 hours in a salt bath furnace). According to this processing condition,
The structure after the treatment becomes lower bainite.

By using carbon steel instead of the conventional chromium steel as the material of the cage 4, the material cost can be reduced as compared with the conventional case. In addition, by adopting an austempering process instead of the conventional carburizing process as the heat treatment of the cage 4, deformation due to the heat treatment is reduced as compared with the conventional case, thereby simplifying the processing for ensuring accuracy after the heat treatment (eg, grinding). Or can be omitted. For example, grinding after heat treatment of the pocket surfaces 4c1 on both sides in the axial direction of the pocket 4c can be omitted. Even in this case, the deformation rate due to the heat treatment is small, so that the defective rate is smaller than in the past. In addition, the grinding process after the heat treatment of the outer diameter surface 4a and the inner diameter surface 4b may be performed only in a region that comes into contact with the outer joint member 1 and the inner joint member 2, or may be omitted in some cases.
Further, by performing the austempering treatment, the structure of the carbon steel becomes bainite, so that the material has excellent toughness and good durability can be obtained.

The present invention is not limited to the double offset type constant velocity universal joint described above, and is similarly applicable to a Zepper type constant velocity universal joint (ball-fixed joint). That is, an outer joint member in which a plurality of curved guide grooves are formed in a spherical inner diameter surface in an axial direction, and an inner joint member in which a plurality of curved guide grooves are formed in a spherical outer diameter surface in an axial direction. A torque transmission ball disposed on each of a plurality of ball tracks in which a guide groove of the outer joint member and a guide groove of the inner joint member are formed in cooperation with each other, and a retainer for holding the torque transmission ball, In a constant velocity universal joint in which a track is opened in a wedge shape toward one side in the axial direction, the retainer can be formed of carbon steel subjected to austempering.

[0021]

EXAMPLE With respect to the cage having the shape shown in FIG. 2, the heat treatment deformation of a carbon steel austempered product (example product) and a chromium steel carburized product (conventional product) were measured. The material of the example product is JIS carbon steel for machine structural use S15C, S35C, S
After heating at 870 ° C. for 25 minutes, each was placed in a salt bath at 350 ° C. and held for 40 minutes (austempering treatment). The material of the conventional product was one type of JIS chrome steel SCr415 and was carburized. Test pieces were manufactured 10 pieces for each of the above 4 types.
The outer diameter, inner diameter, and axial dimension of the pocket of each test product were measured before and after the heat treatment, and the difference between the dimensions was regarded as the heat treatment deformation. The measurement results are shown in FIGS.

As is evident from the measurement results, the heat treatment deformation of the example product is about 1/2 in outer diameter as compared with the conventional product,
It was confirmed that the inner diameter was reduced to about 1/5 to 1/10, and the axial dimension of the pocket was reduced to about 1/5. In addition, when a durability test was performed, the example product showed good durability,
In particular, it was confirmed that the austempered product of S53C can obtain the same level of durability as the conventional product.

[0023]

The present invention has the following effects.

(1) Since carbon steel is used as the material of the cage in place of the conventional chromium steel, the material cost is reduced as compared with the conventional case.

(2) As the heat treatment of the cage, an austempering treatment is adopted instead of the conventional carburizing treatment.
Heat treatment deformation is smaller than before. Therefore, processing (grinding or the like) for ensuring accuracy after the heat treatment can be simplified or omitted.

(3) Since the deformation due to the heat treatment is small, the defective rate is reduced as compared with the prior art.

(4) By performing the austempering treatment, the structure of the carbon steel becomes bainite, so that the material has excellent toughness and good durability can be obtained.

(5) The total time required for the heat treatment can be reduced as compared with the conventional case.

(6) As described above, the cost of the cage can be reduced,
Consequently, cost reduction of the constant velocity universal joint can be achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a constant velocity universal joint according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a retainer.

FIG. 3 is a diagram showing a measurement result of a thermal deformation amount.

FIG. 4 is a diagram showing a measurement result of a thermal deformation amount.

FIG. 5 is a diagram showing a measurement result of a thermal deformation amount.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 outer joint member 1a inner diameter surface 1b guide groove 2 inner joint member 2a outer diameter surface 2b guide groove 3 torque transmitting ball 4 cage

Claims (2)

[Claims] 1. An outer joint member in which a plurality of guide grooves are formed in an inner diameter surface in an axial direction, an inner joint member in which a plurality of guide grooves are formed in an outer diameter surface in an axial direction, and a guide groove and an inner side of an outer joint member. A constant velocity universal joint comprising: a torque transmission ball disposed on each of a plurality of ball tracks formed in cooperation with a guide groove of a joint member; and a retainer for holding the torque transmission ball. A constant velocity universal joint characterized by being formed of carbon steel subjected to austempering. 2. A spherical outer diameter surface guided in contact with an inner diameter surface of an outer joint member, a spherical inner diameter surface in contact with and guided by an outer diameter surface of an inner joint member, and a plurality of torque transmission balls. And a pocket for the constant velocity universal joint, wherein the retainer is made of austempered carbon steel.